In a conventional motion picture film, picture recording regions are arranged in frames at a mid portion of the film. On each side of the picture recording region is a series of evenly-spaced perforations called film take-up holes. This series of take-up holes extends along the longitudinal direction of the motion picture film, that is, along the direction of film travel (the film running direction). A linear analog sound track extends along the film running direction between one side of the picture recording region and that side's corresponding series of take-up holes. Analog audio signals are recorded on this sound track.
Recent progress in digital technology has enabled the digital recording of the contents of this analog soundtrack. Nevertheless, since the recording positions of the picture recording regions and the analog sound track are standardized by the Society Motion Picture and Television Engineers (SMPTE), digitized audio information must be recorded in positions other than the designated recording positions of the picture recording regions and the analog sound track.
Specifically, audio data comprises data for the right channel and data for the left channel. This audio data is recorded in a linear manner in each digital sound track provided along the film running direction between the series of take-up holes and both lateral film edges.
The recorded audio data is arranged in a series of blocks. A synchronization pattern is recorded at the leading end of the series of blocks. A tracking pattern is recorded at the recording start portion and the recording end portion of each block. If each block is thought of as having a horizontal length and vertical height, the horizontal length extends along the film running direction, and the vertical height extends in a direction normal to the film running direction.
The reproducing apparatus reproduces the digital audio data from the motion picture film by using two CCD line sensors provided for optically scanning the digital sound tracks on the motion picture film. Each CCD line sensor has a one-line reading region provided in a direction normal to the film running direction. During reproduction, the light radiated from the back surface of the motion picture film is radiated on each of the reading regions via digital sound tracks formed on the motion picture film. This causes the synchronization data, audio data, and the tracking patterns recorded on the digital sound tracks to be illuminated and radiated on the readout regions of the CCD line sensors.
After CCD line sensors receive the illuminated synchronization data, audio data, and the tracking patterns, they convert these received signals into electrical signals which are routed to a data processor. The data processor reproduces the audio data on a block-by-block basis in synchronization with the synchronization data. The data processor then routes the reproduced audio data to a D/A converter, which converts the audio data into analog audio signals and routes the analog audio signals to a speaker unit. The speaker generates sound in accordance with the received analog audio signals.
The data processor detects the tracking pattern from the CCD line sensor for tracking control. As stated above, the tracking pattern is recorded at the recording start position and the recording end position. Thus, the data processor detects the level difference, for example, between the tracking pattern reproduced at the recording start position and the tracking pattern reproduced at the recording end position, in order to detect any tracking errors. The readout timing of the CCD line sensor is variably controlled in response to the tracking error.
Correcting the tracking error permits the CCD line sensors to read audio data from the center of each data track, instead of from a position that is offset from the center of such tracks.
However, when the tracking pattern is provided at the recording start position and the recording end position for recording audio data, the available space for audio data regions is reduced, and therefore, the amount of audio data is also decreased. Although tracking patterns are necessary for accurately reproducing audio data, the decrease in recorded audio data that results from using tracking patterns in this manner also decreases the reproduced sound quality.